Hillesheim : staining nuclei of fresh-water alg i . 59 



wall with a very few scattered about in the center. The 

 nuclei are extremely numerous, as many as forty-six being 

 counted in a very young coenocyte, while in the mature coeno- 

 cytes there were many hundred. 



Cladophora species. — Both the borax and the ammonia car- 

 mine stains were taken very readily by the nuclei of these 

 plants. The nuclei, however, were brought out more clearly 

 when hematoxylin was used. In a coenocyte of one species 

 thirty-eight nuclei were counted. In another species only six 

 could be made out. The nuclei were mostly spherical in shape. 



Summary. — The best fixing agent for the algae studied was 

 chromic acid. The most successful stain was a mixture of 

 borax and ammonia carmine. 



Explanation of Plate XIV. (in Part). 

 All the drawings were made with the camera lucida. 

 Figure 4. Cell of Spirogyra. Length of cell 100 mic, width of 

 cell 50 mic. Diameter of nucleus, 12 mic, X 193. 



5. Cell of Spirogyra. Shows relative size of nucleus and cell, 

 x 450- 



6. Cell of Zygnenia. Nucleus in resting condition. Diameter of 

 cell 37 mic, length 62 mic. Diameter of nucleus 7 mic, length of 

 nucleus 12 mic, x 450. 



7. Cell of Zygnema. Daughter nuclei, just after division is com- 

 plete, x 193. 



8. Homiiscia zonata (Web. and Mohr. ) Aresch. Diameter of 

 cell 20 mic, length 25 mic. Nucleus 5 mic. in diameter, x 450. 



9. Microspore/, sp. Diameter of cell 10 mic, length 45 mic 

 Diameter of nucleus 5 mic, x 450. 



10. Hydrodictyon reticulatum (Linn.) Lagerh. Diameter of coeno- 

 cyte 11 mic, length 66 mic. Diameter of nuclei 1 mic, X 193. • 



11. Cladophora species. Diameter of coenocyte 63 mic, length 

 150 mic. Diameter of nucleus 7 mic, X 450. 



